Dead Ringers is a 1988 psychological horror film starring Jeremy Irons in a dual role as identical twin gynecologists. Director David Cronenberg co-wrote the screenplay with Norman Snider; their script was based on the novel Twins by Bari Wood and Jack Geasland. The film is very loosely based on the lives of Stewart and Cyril Marcus.
Elliot and Beverly Mantle are identical twins and highly successful gynecologists. Elliot, the more aggressive and confident of the two, seduces women who come to the Mantle Clinic. When he tires of them, the women are passed on to the shy and passive Beverly, while the women remain unaware of the substitution.
When Beverly becomes attached to the troubled actress Claire Niveau (Geneviève Bujold), it upsets the equilibrium between the twins. It turns out that Niveau is a "trifurcate;" she has an abnormal reproductive system. Beverly describes her internal arrangement as having "three doorways," which means she probably will not be able to have children....